Electric heat-producing element and applications thereof to apparatus or articles



E c. H. mums. ELECTRIC HEAT PRODUCING ELEMENT AND APPLICATIONS THEREOFT0 APPARATUS 0R ARTICLES. APPLICATION FILED JUNE 29,1920.

1,404,063. Patented Jan. 17, 1922.

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C. H. RODDIS. moms HEAT rnooucms ELEMENT AND APPLICATIONS THEREOF T0APPARATUS 08 ARTICLES. APPLICATION FILED JUNE 2911920- 1,4()4,063,Patented Jan. 17, 1922.

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UNITED STATES;

garsur OFFICE.

CHARLES HENRY RODDIS, OF BEDFORD, ENGLAND. i

ELECTRIC HEAT-PRODUCING ELEMENT AND APPLICATIONS THEREOF TO APPARATUS ORARTICLES.

Specification of Letters Patent.

Patented Jan. 17, 1922.

Application filed June 29, 1920, Serial No. 392,631.

To all whom it may concern:

Be it known that I, CHARLES Hnnnv Robins, subject of the King of GreatBritain,

residing at 66 Elstow Road, Bedford, in the county of Bedfordshire,England, electrical engineer, have invented certain new and usefulImprovements in Electric Heat-Producing Elements and ApplicationsThereof to Apparatus or Articles, of which the following is aspecification.

My invention provides an improvedelectric heat producingelement'distinctive by the use of carborundum arranged in said elementso that an electric'current is passed through it.

I have ascertained by experiment that commercial carborundum i. e.carborundum in crystal condition initially offers .very great resistanceto the passage through it of an electric current, and that afterbecoming heated develops a negative co-efficient of resistance, that isto say offers less resistance, so that it very quickly heats up and canbe maintained at a given temperature at a low cost of electric power.Said carborundum is preferably a one piece part,

that is to say a block of solid carborundum chipped and hammered to sizeand shape, but it may be composed of a number of fairly large pieces incrystal form suitably held or pressed together without a binding agent,as distinct from granular carborundum.

I have also ascertained that the carborundum block or the like, and theelectrically conductive contacts therewith should be arranged so as tobe capable of being relatively set up to each other either automaticallyas by a spring or by hand to always ensure effective conductivitybetween said contacts and the carborundum, such being very necessarywhere the co-eiiicients of ex pansion and contraction of the carborundumand the contacts are substantially different.

My invention has many applications, such as in a vapourising andignition plug or device for a semi-Diesel engine, as a heat producingelement for a soldering iron, tea-pot, kettle, oven and such like, andas a heat producing element for radiators.

Two applications of the invention are represented by the accompanyingdrawings, one as a vapourising and ignition plug suitable for asemi-Diesel engine, and the other rundum block 'a is the heat producingsub stance arranged within the one end 0 of a steel casing 0 providingthe body of the plug, this casing forming one of the electricalconductors. The centre rod (Z is the other electrical conductor. Saidcarborundumbloc-k is fashioned to size and shape to fit within the end 0of the body which is a closed end as indicated ate but may have a hole 0through 1t, as indicated by the dotted lines, to partly open said end.Said block is substantially circular in cross section as shown in Fig. 3and makes direct conductive contact with the end of the casing and withthe centre rodrl, but it may have applied between its diameter andtheinner sides of the casing end a tubular insertion of mica or asbestos sothat it is substantially insulated from the casing end except at theclosed end wall of the casing or at the end where through the hole 0 isprovided.

Th casing is adapted at 0 for screwing into a hole of the cylinder ofthe semi-Diesel engine in a manner earthing the circuit.

The casing of the plug has applied to its hollow interior a porcelainbush 6 to serve as a mounting for the centre rod (Z which is clamped tothe bush between a. packed collared end (Z of the rod and a clamping nut(Z pulling up with washers cl against the outer end of said bush. Saidbush may be of any insulating material able to withstand heat.

The latter is applied to the casing 0 so as to be advanced towards thecarborundum a by the tubular nut which engages the easing and encirclesthe bush; a packing material 9 being provided between the bush and thetubular nut Therefore the porcelain bush 0 is clamped within the casingbetween the tubular nut f and the inner end of the carborundum a, by theinner end of the V centre rod abutting hard against the carboirundumblock to in turn clamp the carborundum piece'between'its end and theclosed orpartially closed end of the casing.

It will be clear from Fig. 1 that good electrical conductive contactbetween the rod 4, end 0 of the casing and the carborundum block canalways be made by a slight screwing up of the tubular nut f.

' It will be obvious that if a spring washer is combined with thepacking 9 said washer may operate for automatically setting up theconductive contacts to the carborundum in case any looseness shoulddevelopin actual use due to differential expansion and eon- V tractionof the materials in touch.

The lead wire is connected to the outer end of the centre rod d in theordinary way with sparking plugs, it being the binding terminal-torsaidrlead wire. 7

:With reference to Figs. 4 and 5 the carborundum block a is locatedwithin a socketlike carrier 0 suitably attached to some suitable part'dof the heat producing element, but between this carrier and thecarborundum are provided tubular mica or asbestos :lengths e and f, andwithin the bottom of the socket a mica or asbestos disc 9. One ofthe'conductive contacts is a wire it engaging between the disc 9 and theend of the carborundum block a this wire passing at k between'thetubular pieces 6 and f and threading through an insulating bush 2'applied to the socket 0; through which bush also passes the otherconductive contact j which bears hard against the outer end of thecarborundum block a and is set up to it by the action of a 'ringnut Zapplied to the socket to traverse the bush inwardly and maint-ainefiective electrical connection between the wire it and'the rod j. c

Having now described my inventlon what 'I' claim and desire to secure byLetters Patent is 1. An electric rheostat comprising a cas- 7 ing, acarborundum block within said casing, an electrode making pressurecontact with said carborundum block and means for varying the pressureof said contact.

2. An electric rheostat comprising a casing, a ca-rborundum blockcarried within said casing, an electrode making pressure trode beingprovided with a collar intermediate its ends, a bush of insulatingmaterial surrounding said electrode and in abutment with said collar,and a screw threaded gland engaging said receptacle and bush, said glandbeing adjustable for-varying the pressure between said electrode andcarborundum block.

In testimony whereof I have hereunto-set my hand in presence oftwosubscribing witnesses. r

CHARLES HENRY RO'DDIS Witnesses:

GEO. T. F UERY, JOHN P. FUERY.

